Fluorine-containing polymers, or fluoropolymers, are an important class of polymers and include for example, fluoroelastomers and fluoroplastics. Within this class are polymers of high thermal stability and usefulness at high temperatures, and extreme toughness and flexibility at very low temperatures. Many of these polymers are almost totally insoluble in a wide variety of organic solvents. See, for example F. W. Billmeyer, Textbook of Polymer Science, 3rd ed., pp. 398-403, John Wiley & Sons, New York (1984).
Fluoroelastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers, such as hexafluoropropene, have particular utility in high temperature applications, such as seal gaskets and linings. See, for example, Brullo, R. A., "Fluoroelastomer Rubber for Automotive Applications," Automotive Elastomer & Design, June 1985, "Fluoroelastomers Seal Up Automotive Future," Materials Engineering, October 1988, and "Fluorinated Elastomers," Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Vol. 8, pp. 500-515, John Wiley & Sons, New York (1979).
Fluoroplastics, particularly polychlorotrifluoroethylene, polytetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, and poly(vinylidene fluoride), have numerous electrical, mechanical, and chemical applications. Fluoroplastics are useful, for example, in wire, electrical components, seals, solid and lined pipes, and pyroelectric detectors. See, for example, "Organic Fluorine Compounds," Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 11, pp. 20, 21, 32, 33, 40, 41, 48, 50, 52, 62, 70, and 71, John Wiley & Sons, New York (1980).
Increased concerns with evaporative fuel standards have led to a need for fuel system components that have increased barrier properties to minimize the permeation of fuel vapors through automotive components such as fuel filler lines, fuel supply lines, fuel tanks, and other components of the emission control system of the engine. Various types of tubing have been proposed to address these concerns. In general, the most successful of these have been co-extruded multi-layer tubing.
Multi-layer compositions comprising a fluorinated polymer layer and a polyamide or polyolefin layer are known. See, for example, U.S. Pat. No. 4,685,090 (Krevor) which discloses laminate tubular articles which can comprise layers of fluorocarbon elastomers, and PCT Publication WO 93/1493 (LaCourt) which discloses a laminar film structure comprising a polyimide and a fluoropolymer. The use of fluorinated polymers in retroreflective sheeting is also known. See for example U.S. Pat. Nos. 3,551,025 and 4,348,312 for products including glass microspheres, and PCT WO 95/11466 and WO 95/11464 for products containing retroreflective cube corner arrays.
A variety of methods have been used to increase the adhesion between a fluorinated polymer layer and a polyamide or polyolefin layer. For example, an adhesive layer can be added between the two polymer layers. U.S. Pat. No. 5,047,287 discloses a diaphragm, suitable for use in automotive applications, which comprises a base fabric having bonded to at least one surface a fluororubber layer by an adhesive which includes an acrylonitrile-butadiene or acrylonitrile-isoprene rubber having an amino group. See also, for example, European Patent Application 05595445 (Nishino et al.), UK Patent 2,204,932 (Washizu). See also U.S. Pat. No. 5,242,976 (Strassel et al.) which discloses coextruding vinylidene polyfluoride with an alkyl polymethacrylate and vinylidene polyfluoride composition.
Sometimes surface treatment of one or both of the layers is used to help increase bonding. For example, fluoropolymer layers have been treated with charged gaseous atmosphere followed by applying a layer of a second material, for example thermoplastic polyamide. See, for example, European Patent Applications 0185590 (Ueno et al.) and 0551094 (Krause et al.) and U.S. Pat. Nos. 4,933,060 (Prohaska et al.) and 5,170,011 (Martucci).
Blends of the two layers are sometimes used as an intermediate layer to help bond the two layers together. European Patent Application 0523644 (Kawashima et al.) discloses a plastic laminate having a polyamide resin surface layer and a fluororesin surface layer. The application states that it is difficult to make laminates having a polyamide layer and a fluororesin layer due to the incompatibility of the two materials. The laminate is prepared by the use of an intermediate layer of a blend of an aliphatic polyamide resin with a fluorine-containing graft copolymer.